How to change PO pricing conditions programmatically - User exit ?

I need to add PO pricing condition while saving new PO via ME21, to
automate Freight Cost input.
I'm trying to use PO user exit, which generate include program ZXM06U44,
but the additional entry of XKOMV is not added to pricing condition.

Please kindly advise, how can I achieve that kind of automation in SAP.